The present invention relates to the method of manufacturing a hydrorefining catalyst, in particular relates to the method of manufacturing a catalyst suitably employed in the hydrodesulfurization process which comprises treating a hydrocarbon feed stock containing a sulfur compound and a relatively large amount of contaminants that deactivate the catalytic composite, in particular a residual oil, in the presence of hydrogen.
In general, the hydrorefining catalyst comprises carrying a hydrogenating metal component on a porous alumina. Said hydrogenating metal component includes one metal component selected from Group VIB and one or more of metal components selected from Group VIII of Periodic Table. The activity of the hydrorefining catalyst deteriorates, in the initial stage of treating a heavy hydrocarbon oil, mainly due to the separation of carbonaceous substances on the catalyst surface, said carbonaceous substances being resultant from decomposition of asphaltenes contained in the feed stock, and the activity more deteriorates as the treating time is prolonged. This is because vanadium and nickel compounds bound with asphaltenes come to deposit on the catalyst surface with the lapse of time. Accordingly, in proportion to the tendency that the hydrocarbon feed stock is becoming heavy, there is an aceute demand for a hydrorefining catalyst that is resistable against metal contaminants containing vanadium and nickel and is capable of holding a high desulfurization activity for a long period of time.
The activity of the catalyst utilized in catalytic hydrorefining, in particular hydrodesulfurization, of heavy hydrocarbon oils is in close contact with the pore volume, pore distribution and pore diameter of the catalyst, and the pore distribution and pore diameter of the catalyst are, as a matter of course, influenced by the pore volume, pore distribution and pore diameter of the porous alumina utilized as the carrier material for the catalyst. Generally speaking, the porous alumina utilized as the carrier material for the hydrorefining catalyst may be made from pseudo-boehmite, but Japanese Patent Publication No. 35893/1981 Specification discloses that the use of an alumina hydrate containing a pseudo-boehmite having a crystal size grown in the range of 40-80 A as a precursor of a porous alumina permits to obtain alumina wherein the greater part of the total pore volume is occupied by pores having a pore diameter of 600 A or less.
On the other hand, Japanese Laid Open Patent Application No. 27036/1980 Specification discloses a hydrodesulfurizing catalyst comprising a porous alumina carrier and Group VIB and VIII metal components carried thereon, wherein the average pore diameter measured by nitrogen adsorption method is in the range of 100-130 A and the pore volume of pores having a diameter of 90-140 A occupies 70% of the pore volume of pores having a diameter up to 600 A, and mentions that this hydrodesulfurizing catalyst can exhibit a high desulfurizing activity because it prevents entrance of asphaltenes bound with metal contaminants into pores.